Mar 6 - McClatchy-Tribune Regional News - Bob Audette Brattleboro Reformer, Vt.



A hole discovered in a pipe in Vermont Yankee's off gas building could be partly to blame for the leakage of tritiated water into the ground beneath the nuclear power plant in Vernon, said Bill Irwin, Vermont's chief of radiological health.

"I have been told by Entergy officials that the leak rate from the hole in this pipe is sufficient to generate the 100 gallons per day currently running through the floor drain to the off gas pit sump and to the radioactive waste building," said Irwin. "I would assume that if the floor drain was clogged, as it was until Feb. 14, that this 100-gallons-per-day leak rate is sufficient to have contributed at least partly to the groundwater contamination on site."

 An inspection of the pipe tunnel conducted by a remotely operated vehicle on Friday revealed "a dime/quarter size hole" at an elbow in a 1 to 1.5 inch diameter off gas drain line, stated Larry Smith, Yankee's director of communications, in an e-mail to the media.

Using the ROV, technicians discovered water and steam coming from the hole, stated Smith.

"The visual inspection results will be used in conjunction with plant drawings to identify which of several pipes running through this area is at fault," he stated.

The plant diagrams will also be used to determine the pipe's pathway within the pipe tunnel.

The water in the tunnel is being processed "through plant systems as designed," stated

Smith.

During inspections of the exterior of the pipe tunnel, Entergy workers discovered a crack in a concrete casing around the off gas drain line.

Even though water leaked from the crack during a test last week , it is not yet known if it's the source of the tritiated water because there has been no leakage observed during normal operation of the plant, stated Smith.

But Irwin said the crack could be "sufficient to have introduced this contaminated water into the ground from the off gas pipe tunnel."

The tritium concentration in water draining from the pipe tunnel prior to the unclogging of the tunnel's floor drain was similar to the concentration found in a monitoring well located next to the off gas building, he said.

"All of this, along with the radioactivity found in the soil near the leakage pathway and the continuously declining tritium concentrations at the well is solid evidence that this is at least one leakage pathway for radioactively contaminated water into the environment," said Irwin.

However, he said, work still needs to be done to determine whether any other potential sources have not contributed to the contamination of the groundwater.

Yankee engineers continue to install new monitoring wells to determine how big the plume of contamination is and where it is headed.

Initial results indicate that the plume is headed toward the Connecticut River, though New Hampshire's public health director, Jose Montero, said Thursday that no tritium has yet been found in the river.

Other wells are being drilled to determine the nature of the bedrock under the plant to help hydrologists better understand how groundwater flows beneath the site.

Shallow wells, at about 30-feet deep, are showing higher tritium concentrations than deeper wells, at about 70-feet deep, stated the Vermont Department of Health, in its daily update posted on its Web site.

A deep well located at what is assumed to be the centerline of the underground plume has a tritium concentration of 2,300 picocuries per liter.

A shallow well located next to the deep well has concentrations of 144,000 picocuries, stated the DOH.

"While this is still early in this well's history, it is clear that there are differences in tritium concentrations nearer and farther from the ground," stated the DOH.

Tests of water samples for "hard to detect" materials such as strontium-90, iron-55 and nickel-63 have so far turned up no evidence of contamination.

All on-site and off-site drinking water well samples continue to show no tritium in excess of the lower limit of detection, stated the DOH, and no on-site or off-site wells show any other radioactive materials related to nuclear power plant operations.

Bob Audette can be reached at raudette@reformer.com, or at 802-254-2311, ext. 273.

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